This invention relates to a compositions and methods of repelling insects, and more particularly to methods for repelling mosquitoes and biting flies, such as ceratopogonid flies, using a natural ingredient, emu oil, active fractions thereof and compositions comprising emu oil or active fractions thereof and at least one other insect repellent such as citronella or DEET, optionally, further comprising saponin.
Known natural oils that repel insects include rotundial (from the leaves of Vitex rotundifolia, Watanabe K et al. (1995) Biotech Biochem 59(10):1979-1980); citronella oil (e.g. U.S. Pat. No. 5,346,922); eucalyptus oil (Watanabe et al. (1993) J Agric. Food Chem. 41:2164-2166); neem oil (Sharma VP et al (1993) J American Mosquito Control Association 9(3):359-360); and oil of Hedeoma pulgioides, oil of anisum and oil of chrysanthemum (U.S. Pat. No. 5,208,209). Another natural oil that has repellent activity is saponin (Croda from Sapindus). Saponin has been shown to repel lice and also serves to improve the spreading consistency of repellent compositions and reduce greasiness.
However, the compound most widely used as a topically-applied insect repellent is N,N-diethyl-m-toluamide (DEET). When applied to children's skin, DEET has been implicated in causing convulsions. DEET is also known to react with certain plastics and synthetic rubber and cause skin irritation (Watanabe et al. (1993), supra). As a result of these problems and other side effects, New York State had banned products comprised of 100% DEET.
The active fractions of the naturally occurring insect repellents are also largely unknown. Methods of resolving heterogeneous compounds into chemical species are well-known in the art. For example, silica gel flash chromatography provides for high speed resolution of organic compounds (see, e.g., U.S. Pat. No. 4,293,422). After separation, the eluted fractions can be recovered and tested for the activity of interest.
Accordingly, there remains a need for a natural, safe substance which acts to repel biting insects when topically applied to the skin. The active fraction(s) of such a substance is also needed as are effective compositions comprising emu oil or active fractions thereof and compositions comprising emu oil or active fractions thereof in combination with at least one other insect repellent such as citronella, DEET or saponin.